Various types of flight vehicle structures such as rockets, missiles, satellites, and the like are typically configured in a plurality of stages. When in use, these vehicle flight structures oftentimes need to separate one stage from another on command at a specific time during vehicle flight and relatively instantaneously while having the separated stage drop off from the remainder of the flight vehicle structure and while also maintaining complete confinement of any explosive debris. One commonly used device for selectively separating one stage from another is a frangible separation joint.
Various types of flight vehicle structures such as rockets, missiles, satellites, cargo hold/payload, also contain fairing/body panels used to protect internal components that later need to be uncovered. When in use, these vehicle flight panels oftentimes need to separate from the vehicle and another on command at a specific time during vehicle flight and relatively instantaneously while having the separated panels drop off from the flight vehicle structure and while also maintaining complete confinement of any explosive debris. One commonly used device for selectively separating fairing/body panels from another is a frangible separation joint.
Such a frangible separation joint is commonly in the form of a ring or rail that is mechanically connected (e.g., bolted) to the two vehicle stages or fairing panels and located there between along the entire outer circumference of both stages. The separation joint typically contains an expansion device or confinement tube located within a receiving channel and commonly made from a metal such as aluminum or stainless steel. The expansion device contains an elastomeric material (e.g., silicone rubber) with at least one hole formed there through that contains an explosive charge, such as a mild detonating fuse that runs the entire length of the separation joint (i.e., a linear explosive charge).
The frangible joint also typically has an initiation manifold located at a point along its circumferential length. The initiation manifold typically contains one or more electrical wires that connect the explosive charge to a charge detonation control device (e.g., a flight vehicle computer). Upon the selective commanded detonation of the explosive charge at the appropriate time during vehicle flight, the shock from the explosion is transmitted to the expansion device or confinement tube which subsequently fractures a separation ring along a stress riser, rupture groove or fracture seam (e.g., one or more grooves). The fracture seam thus forms a line of separation between the two stages of the flight vehicle. Typically, complete confinement of the explosive by-products or debris is maintained by the confinement tube and associated explosive initiation manifold. Also, no secondary fracturing of the flight vehicle structures desirably occurs. Once the separation ring fractures upon detonation of the explosive material, complete separation of the two stages of the flight vehicle structure previously held together by the frangible joint has taken place such that one stage falls away from the remainder of the flight vehicle structure, which then continues on in its flight.
Problems with such a frangible separation joint include the fact that the silicone rubber charge holder tends to thermally contract and/or undergo acceleration compression or deformation during the various stages of flight of the flight vehicle structure. As a result, a less than desired amount of mechanical retention of the silicone rubber charge holder within the metal confinement tube occurs. That is, the silicone rubber charge holder tends to move and/or deform during vehicle flight. Also, a relatively large mismatch of the coefficients of thermal expansion occurs between the silicone rubber charge holder and the surrounding aluminum or stainless steel confinement tube. This causes a lack of control of the expansion and contraction between the silicone charge holder and the surrounding metal confinement tube during the various stages of flight of the flight vehicle structure.
What is needed is an improved frangible separation joint of the type mentioned herein above that eliminates the problems discussed herein above of such prior art frangible separation joints.